Referring to FIG. 1, there is shown a top view of a conventional tape running system (schematic) in a VCR. The VCR tape loading mechanism is a mechanism to draw out a tape 11 accommodated in a VCR cassette 10 and leads to a drum 1 having rotating heads thereon to slip halfway round the drum 1 at a predetermined position and angle of entry and leaving.
Shown in FIGS. 2 and 3 are the construction of above mentioned conventional VCR tape loading mechanism.
The slant posts 4a and 4a that draw out a VCR tape respectively are positioned in the upper surfaces of slant bases 4 and 4 respectively adapted to move along the guide grooves 3 and 3 respectively.
One end of the second loading levers are connected to the slant bases 4 and 4 respectively and the other ends are pinned to one end of first loading levers 6 and 6 respectively to move around them.
The other ends of the first loading levers 6 and 6 are fixed at shafts 5a and 5a of loading gears 5 and 5 respectively.
A sector gear 8 has gear teeth 8a in one end and a pin 8b in the other end and the gear teeth 8a are meshed with the gear teeth of one of the loading gears 5 and 5.
The power of a loading motor 14 is transmitted to a worm 10 through a motor pulley 13, a belt 12, and a worm pulley 11, The worm 10 rotates a cam gear 9 having a cam groove 9a on the surface.
The pin 8b of sector gear 8 is inserted in the cam groove 9a of the cam gear 9.
Torsion springs 18 and 18, being engaged, positioned coaxially between the loading gears 5 and 5 and the first loading levers 6 and 6 respectively, pushing the first loading levers 6 and 6 against stoppers 5b and 5b respectively provided on the loading gears 5 and 5 respectively (Refer to FIG. 7)
Referring to FIG. 1, the loading operation of a VCR tape running system, equipped with above mentioned VCR tape loading mechanism, is as follows;
A VCR tape 11 wound on reels 10a and 10a accommodated in a cassette 10 is, drawn out by the slant posts respectively, slipped half way round a drum 1 having rotating heads thereon at a predetermined angle of entry and leaving, and transmit electric signals to the rotating heads during reproduction. Meanwhile as known well, the tape is transferred by a capstan shaft 15 and a pinch roller 16.
Referring to FIG. 2 and FIG. 3, the operation of above mentioned VCR tape loading mechanism will be described.
Shown in FIG. 2 is unloaded condition, where the first loading levers 6 and 6 are in contact with the stoppers 5b and 5b of the loading gears 5 and 5 respectively.
Referring to FIG. 3, the description will be focused on the loading operation first.
During loading operation, the loading motor 14, upon rotation in clockwise direction seen from the pulley 13 side, rotates the cam gear 9 in counter clockwise direction through the motor pulley 13, the belt 12, the worm pulley 11 and the worm 10, and the pin 8b of the sector gear 8 is inserted in cam groove 9a rotates in clockwise direction following the displacement of the cam groove 9a.
When one of the loading gears 5 and 5 meshed with the teeth of the sector gear 8 rotates in counter clockwise direction, the other loading gear 5 rotates in clockwise direction, and the first loading levers 6 and 6 rotate accordingly.
The slant bases 4 and 4 move along the guide grooves 3 and 3 respectively in response to the movements of the first loading levers 6 and 6 respectively and the second loading levers 7 and 7 respectively.
When the slant bases 4 and 4 come to a loading completion position respectively, where the stoppers 2 and 2 respectively hold any further movement of slant bases 4 and 4 respectively, the respective positions of the first loading levers 6 and 6 and the second loading levers 7 and 7 are fixed accordingly. Thereafter when the loading gears 5 and 5 respectively keep on rotating further than above loading completion position, the stoppers 5b and 5b of the loading gears 5 and 5 respectively leave the first loading levers 6 and 6 respectively making the respective spring forces of the engaged torsion springs push the first loading levers 6 and 6 respectively to push the slant bases 4 and 4 respectively against respective stoppers 2 and 2.
The unloading operation is carried out by the reversal of the loading motor 14 making above described loading movement in opposite direction.
In the meantime, referring to FIGS. 8(a) and (b), there are shown load-time curves of the supply loading gear and take-up loading gear respectively, of a conventional VCR tape loading mechanism wherein the maximum electric current of the loading motor is increased suddenly (Refer to FIG. 8(c)) because the starting of pushing by respective slant bases 4 and 4 against respective stoppers 2 and 2 are the same thereby the loads from respective loading gears 5 and 5 exerted on the loading motor 14 are the same too.
Consequently the loading motor 14 requires larger capacity, which causes cost increase to make the product having the larger capacity motor smaller, especially in the case of a camcorder it causes functional problem due to the unavoidable limit of driving power source.